LTC3900_1 Datasheet, PDF (3/20 Pages) Linear Technology – Synchronous Rectifier Driver for Forward Converters

LTC3900
Electrical Characteristics The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T_A = 25°C. V_CC = 5V unless otherwise specified. (Notes 2, 3)
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
t_TMRDIS
V_TMRMAX
Timer Discharge Time
Timer Pin Clamp Voltage
C_TMR = 1000pF, R_TMR = 4.7k
C_TMR = 1000pF, R_TMR = 4.7k
l
40
120
ns
2.5
V
Current Sense
I_CS+
I_CS–
V_CSMAX
V_CS
CS⁺ Input Current
CS^– Input Current
CS⁺ Pin Clamp Voltage
Current Sense Threshold Voltage
V_CS+ = 0V
V_CS– = 0V
I_IN = 5mA, V_SYNC = –5V
V_CS– = 0V
LTC3900E/LTC3900I (Note 5)
LTC3900H/LTC3900MP (Note 5)
l
±1
µA
l
±1
µA
11
V
7.5
10.5 13.5
mV
l
3
18
mV
l
1
20
mV
SYNC Input
I_SYNC
SYNC Input Current
V_SYNC = ±10V
l
±1
±10
µA
V_SYNCP
SYNC Input Positive Threshold
SYNC Positive Input Hysteresis
(Note 6)
l 1.0
1.4
1.8
V
0.2
V
V_SYNCN
SYNC Input Negative Threshold
SYNC Negative Input Hysteresis
(Note 6)
l –1.8 –1.4 –1.0
V
0.2
V
Driver Output
R_ONH
Driver Pull-Up Resistance
I_OUT = –100mA
LTC3900E/LTC3900I
LTC3900H/LTC3900MP
0.9
1.2
Ω
l
1.6
Ω
l
2.0
Ω
R_ONL
Driver Pull-Down Resistance
I_OUT = 100mA
LTC3900E/LTC3900I
LTC3900H/LTC3900MP
0.9
1.2
Ω
l
1.6
Ω
l
2.0
Ω
I_PK
Driver Peak Output Current
Switching Characteristics (Note 7)
(Note 6)
2
A
t_d
SYNC Input to Driver Output Delay
C_FG = C_CG = 4700pF, V_SYNC = ±5V
LTC3900E/LTC3900I
l
60
120
ns
LTC3900H/LTC3900MP
l
150
ns
t_SYNC
Minimum SYNC Pulse Width
V_SYNC = ±5V
l 75
ns
t_r, t_f
Driver Rise/Fall Time
C_FG = C_CG = 4700pF, V_SYNC = ±5V
15
ns
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC3900 is tested under pulsed load conditions such that
T_J ≈ T_A. The LTC3900E is guaranteed to meet performance specifications
from 0°C to 85°C operating junction temperature. Specifications over
the –40°C to 125°C operating junction temperature range are assured
by design, characterization and correlation with statistical process
controls. The LTC3900I is guaranteed over the –40°C to 125°C operating
junction temperature range. The LTC3900H is guaranteed over the full
–40°C to 150°C operating junction temperature range. The LTC3900MP
is guaranteed and tested over the full –55°C to 150°C operating junction
temperature range. High junction temperatures degrade operating
lifetimes; operating lifetime is derated for junction temperatures greater
than 125°C. Note that the maximum ambient temperature consistent
with these specifications is determined by specific operating conditions
in conjunction with board layout, the rated package thermal impedance
and other environmental factors. The junction temperature (T_J, in °C) is
calculated from the ambient temperature (T_A, in °C) and power dissipation
(P_D, in watts) according to the formula:
T_J = T_A + (P_D • θ_JA), where θ_JA (in °C/W) is the package thermal
impedance.
Note 3: All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to ground unless otherwise
specified.
Note 4: Supply current in normal operation is dominated by the current
needed to charge and discharge the external MOSFET gates. This current
will vary with supply voltage, switching frequency and the external
MOSFETs used.
Note 5: The current sense comparator threshold has a 0.33%/°C
temperature coefficient (TC) to match the TC of the external MOSFET
R_DS(ON).
Note 6: Guaranteed by design, not subject to test.
Note 7: Rise and fall times are measured using 10% and 90% levels. Delay
times are measured from ±1.4V at SYNC input to 20%/80% levels at the
driver output.
3900fb
3